Apparatus for vacuum metallizing

ABSTRACT

Vacuum metallizing apparatus wherein metal contained in a crucible in a vacuum chamber is melted to form vapor adapted to metallize a continuously moving web of sheet material with metal vapor as it moves therepast and having means to direct such vapor only onto preselected portions of the web, such means including a vapor masking means positioned between the crucible or vapor supply source and the web and consisting of a heat conductive frame having slots therein for receiving vapor masking ribs (of various shapes), which ribs are slidably positioned in thermal contact with the frame, in the slots. The frame is cooled by cooling means connected to it, which cooling means also cool the masking ribs of the vapor masking means by reason of the thermal contact between the frame and the ribs. Connecting material may be inserted between the ribs and the surface portions of the frame defining the slots to thermally connect the ribs to the cooling means.

United States Patent Carleton [$4] APPARATUS FOR VACUUM METALLIZING 72 Inventor: John '1. (3811211)", Arlington, Ohio [73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Feb. 19, 1971 [2|] Appl. No.: 117,012

[521 US. Cl ..118/48 [51] Int. Cl ..C23c 13/08 [58] Field of Search ..l l8/48-49.5, 503,

[56] References Cited UNITED STATES PATENTS 3,044,438 7/ I962 Osswald et al 1 18/491 3,121,852 2/1964 Boyd et a]. ..1 18/495 UX 3,241,519 3/1966 Lloyd ..1 18/49 3,323,490 6/1967 McGilliard I 18/504 Primary Examiner-Morris Kaplan Attorneyl-loge T. Sutherland 51 Aug. 15, 1972 i 1 ABSTRACT Vacuum metailizing apparatus wherein metal contained in a crucible in a vacuum chamber is melted to form vapor adapted to metallize a continuously moving web of sheet material with metal vapor as it moves therepast and having means to direct such vapor only onto preselected portions of the web, such means including a vapor masking means positioned between the crucible or vapor supply source and the web and consisting of a heat conductive frame having slots therein for receiving vapor masking ribs (of various shapes), which ribs are slidably positioned in thermal contact with the frame, in the slots. The frame is cooled by cooling means connected to it, which cooling means also cool the masking ribs of the vapor masking means by reason of the thermal contact between the frame and the ribs. Connecting material may be inserted between the ribs and the surface portions of the frame defining the slots to thermally connect the ribs to the cooling means.

7 Claims, 5 Drawing Figures PAIENTEnnus 15 1912 3.683; 847

sum 1 or z 4 2| FI'GJ INVENTOR JOHN T. CARLETON W a-Jmq ATTORNEY APPARATUS FOR VACUUM METALLIZING BACKGROUND OF THE INVENTION of various shapes and sizes, which masking ribs may be easily interchanged to define various deposition patterns in a manner and using structure to assure their proper operation.

2. Description of the Prior Art The use of vapor masking means in vacuum metallizing apparatus is old.

In the preparation of metallized films with lane patterns for use in capacitors, it is known, for example, to position a mask, with non-interchangeable parts, over the moving film, during metallization, to define the desired pattern. A great number of masks, however, are required to provide the different lane spacings and make economical use of the metallizing apparatus. This is a problem.

A mask with interchangeable parts permits a reduction in the number of separate patterns required but the adjustment of the masking parts or ribs often is time consuming and there is a tendency for the ribs in the larger masks to distort as a result of heating of the mask's bars.

U. 8. Pat. No. 3,241,519 to Lloyd is exemplary of the prior art teachings. It discloses a mask interposed between a vapor source and a moving substrate in which tensioning means in the form of screws (two for each bar) are provided for applying tension to thin masking bars. Cooling means are provided in the frame for cooling the frame.

While these features may prevent thin masks from sagging and permit accurate coating of a moving substrate, they greatly increase, for example, the time required to interchange (and correctly position) masking bars one for another, with proper tensioning, etc., and thereby decrease the flexibility of the metallizing operation.

The solution to these problems is a novel vapor masking means with a heat conductive frame having slots therein in which vapor masking elements or ribs may be slidably, removably, positioned in thermal contact with the frame (whereby it is cooled) to provide a masking means which can rapidly be set up with different patterns and is free from distortion in use.

The slidable, positioning capability of the masking -ribs of the instant invention, enables great ease of interchange with immediate, assured, thermal connecting of the masking ribs to other operative parts of the apparatus.

SUMMARY OF THE INVENTION The vacuum metallizing apparatus of this invention provides a novel vapor masking means for controlling or preselecting various patterns of metallization by sliding masking ribs of desired shape into position in slots in a frame.

Briefly described in this invention, a crucible containing metal to be vaporized is positioned within a vacuum chamber of the vacuum metallizing apparatus. A masking means, in the form of a frame with interchangeable masking ribs, is positioned adjacent the web of material to be metallized and between it and the vapor source. By inserting masking ribs of the desired configuration into slots in the frame, various vapor deposition patterns may be realized.

In greater detail, an apparatus of this invention for vacuum metallizing a web of sheet material comprises:

a vacuum chamber adapted to being evacuated of its atmosphere;

a web supply source, a web windup roll and means to move the web from the supply source and onto the windup roll;

a vapor supply source including a crucible containing metal located within the chamber;

means to melt the metal in the crucible to form vapor to metallize an exposed surface of the web as the web is moved past the crucible;

a vapor masking means positioned between the vapor supply source and the web being metallized, such masking means consisting of:

a heat conductive frame having opposed side members each having inner surface portions defining slots therein,

heat conductive cooling means connected to outer surface portions of the opposed sides,

heat conductive cooling means connected to outer surface portions of the opposed sides,

heat conductive vapor masking ribs each having surface portions defining rib positioning parts slidably positioned in opposed slots to lock the masking ribs in position with respect to the web,

the surface portions defining the slots and defining the rib positioning parts being in thermal contact with each other whereby the masking ribs and the frame are cooled by the cooling means connected to the frame.

Preferably, a heat conductive connecting material is inserted between the rib positioning parts of the masking rib and the inner surface portions of the side members defining the slots in the frame thereby thermally connecting the masking ribs to the cooling means. A suitable connecting material is graphite dust, which, if desired, may be contained in a non-volatile oil, for ease of application.

The heat conductive frame preferably is fixedly positioned adjacent to, and at a predetermined spaced distance from, the web. The heat conductive cooling means are connected to the frame to cool it during the metallizing operation and the masking ribs are slidably positioned in the slots to lock the specific or various patterns of the ribs desired in position with respect to the web. Vapors passing through openings defined by these ribs define the pattern of metallizing. The surface portions defining the slots in the frame and defining the rib positioning parts which are slidably received in these slots are in "thermal contact" with each other so that the cooling means connected to the frame also will effectively cool the ribs during the metallizing operation.

With proper tolerances, the slidable, abutting contact between the rib positioning parts and the surface portions defining the slots will provide adequate thermal contact; however, in some instances, the fit is not within the proper tolerances for cooling (the rib positioning parts may be tapered, for example, to prevent adequate contact between them and the surface portions defining the slots). In these instances, unsuitable thermal connections may be established to properly cool the masking means, and particularly the masking ribs, which condition can be very dangerous and which, certainly, will render the metallizing operation inefiective.

To overcome this problem, a conductive connecting material preferably is provided to operatively connect, beyond question, the masking ribs to the frame and, hence, to the cooling means connected to the frame. The connecting material is preferably in powdery form and is inserted between the rib positioning parts and the slot surfaces. The material may be in a liquid bath which is rubbed on the rib positioning parts of the rib or on the inner surface portions of the side members defining the slots. This connecting material serves, unquestionably, to provide for proper cooling of the ribs, during metallizing.

By also providing means whereby the masking ribs are positioned a predetermined distance from the web, it is a simple matter to exchange various ribs by simply sliding them in and out of the slots, using connecting material where needed to provide proper thermal con nections and using the structure of the rib inserted and the slot structure to provide proper positioning of the parts.

A vapor masking means with easily interchangeable masking ribs is desirable primarily because a variety of capacitor widths may be metallized using such means. This is cheaper than providing different masks for each size capacitor.

A number of requirements are for sizes of capacitors that cannot be made efficiently with masking ribs which can be positioned only in increments of onefourth inch. This requires that an equal number of film rolls of some odd size must be metallized simultaneously in order to produce sizes other than multiples of one-eighth inch.

This invention provides interchangeable masking ribs of novel shapes for forming non-metallized lanes in capacitor film, in which the masking ribs of the desired configuration are positioned in the slots in the supporting frame. The problem of indexing the masking ribs at intervals smaller than the width of the slots is solved by fabricating the slots and the ends of the masking ribs to the smallest practical dimension (one-eighth inch) and by providing several configurations of ribs in which the ends or positioning parts of the rib are offset from the main body or masking part of the rib. This provides even more flexibility in capacitor size selection.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective diagrammatic view of a vacuum metallizing apparatus of this invention, with parts omitted for clarity, showing a web of sheet material being selectively metallized in a vacuum chamber by metal vapor which passes through openings in a vapor masking means positioned between a vapor supply source and the web.

FIG. 2 is a perspective view of a frame of a masking means of this invention showing opposed slots for receiving the various shaped masking ribs which perform the primary masking function of such invention.

FIG. 3 is a perspective view of a typical masking rib of this invention consisting of rib positioning parts and a main masking part.

FIG. 4 is a diagrammatic plan view showing various shaped masking ribs in position in slots in a frame of the type shown in FIG. 2.

FIG. 5 is a fragmentary view showing one end of a masking rib positioned in a slot with connecting material between the surface portions of the side member defining the slot and the surface portions defining the rib positioning parts of the masking rib, which connecting material connects the masking rib to the frame.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and FIG. 1 in particular, a web 10 of sheet material (such as plastic film) to be coated or metallized by the web coating or vacuum metallizing apparatus of this invention is supplied from a web supply source, such as supply roll 1 l, and moved into operative association with means for metallizing the web in a manner to be described. From the supply source II, the web or substrate 10 passes over a transfer roll 12, around a quench drum or web support means 13, and from the drum 13 over a transfer roll 14 and onto a web windup roll 15, all of which parts may be appropriately mounted in a vacuum chamber of the metallizing apparatus of this invention, as is known.

A gas impervious body member or wall 17, with appropriate openings, defines and forms the vacuum chamber 16. Within the vacuum chamber 16 and mounted on appropriate support means 18 is a container or crucible 19 in which is contained material to be vaporized so as to produce metal vapor 20 for metallizing the moving web 10 upon application of a vacuum.

The container or crucible 19, wherein the material or metal to be vaporized is located, has a mouth or opening positioned near the lower portion of circumference of the quench drum 13 which positions the moving web 10 adjacent the crucible opening during the metallizing operation. The crucible 19 has therein a pool of the material, such as molten aluminum in the appropriate position to supply the stream of aluminum vapor 20 upwardly to condense on the moving web 10 upon the melting of the material.

Appropriate means, not shown, are provided to vaporize or melt the metal in the crucible [9. The metal, upon vaporization, deposits and condenses on the web 10 on the lower surface of the quench drum 13 near the outlet of the crucible where it condenses to form a coating. To assist condensation, the quench drum [3 can be provided with an internal coolant as is known.

The vacuum chamber 16 is coupled through a port 2] to a source (not shown) of high vacuum for evacuating the vacuum chamber 16 as is known in the art.

In the operation of the apparatus schematically illustrated, the web 10 which may be paper, plastic or the like, is passed around the quench drum 13, positioned between the supply roll 11 and the windup roll 15 in the chamber. The web 10 can be introduced from the outside through appropriate seals (not shown) or it can be mounted in the vacuum chamber 16. The vacuum chamber 16, where the vapor coating of the web 10 occurs is preferably pumped down by pump to a pressure of less than 1 micron Hg Abs.

The surface of the metal, such as aluminum, in the crucible 19 is raised to a very high temperature on the order of 1,200 to 1,300" C., so copious quantities of aluminum vapor 20 are released. Due to the high vacuum in the vacuum chamber 16, the aluminum vapor 20 travels in substantially straight lines from the surface of the aluminum pool. Most of the vapor 20 condenses on the web as it is moved around the quench drum 13 and adjacent the top opening of the crucible 19 containing the metal.

in order selectively to metallize the web 10, in lanes of given dimensions, for example, a novel vapor mask ing means 30 of this invention is positioned between the crucible 19 and the web 10 being coated. Such masking means 30 consists of a heat conductive frame 31 having front and back members 32 and 33 connected to opposed side members 34 each of which has inner surface portions 35 defining slots 36 therein. The frame 31 is fixedly positioned adjacent to and a predetermined spaced distance from the web 10, and heat conductive vapor masking ribs 37 having rib positioning parts 38 are slidably positioned in the slots 36 therein to lock the ribs 37 in position with respect to the web 10. The surface portions 35 defining the slots 36 and the surface portions 39 defining the rib positioning parts 38 of the ribs 37 must be in thermal contact with each other whereby the ribs 37 and the frame 31 both may be effectively cooled by cooling means 40 connected to outer surface portions 43 of the side members 34 of the frame 31, as will further be explained.

The frame 31 preferably rests on eccentric shafts 41. Turning these shafts raises or lowers the masking means 30 with respect to the web 10 and the drum 13. In the lowest position, the masking means 30 can be easily removed from the metallizer chamber for cleaning or adjustment of the ribs 37 It is advantageous to have control over raising and lowering the masking means from the exterior of the chamber 16 by means of rods (shown in part) or sleds, screw, or other suitable mechanism as is known. As deposition proceeds, metal tends to build on the ribs 37. Longer runs may be made with maintenance of lane integrity if the masking means 30 is slowly backed away from the drum 13 toward the crucible 19.

The metal may be heated by any suitable means, such as induction, heating electron beam, resistance heating, or laser. It may consist of one or more crucibles. if one source is used, it is preferred that it be of the elongated trough type perpendicular to the length of the ribs 37 and approximating the length of the masking means 30 so that the shadow effect of the ribs 37 will be a minimum.

In order to provide adequate cooling, the cooling means 40, consisting of pipes of heat conductive material, such as metal, are conductively cemented or soldered to the side members 34 of the frame 31 which frame is also constructed of thermally resistant and conductive material, such as copper.

It is important that the ribs 37 must make good thermal contact with the inner surface portions 35 of the slots 36. In a vacuum, no gas is present to aid in the transfer of heat. To this end, the clearance tolerances are set at 10 mils or less. It is particularly important that the main surface portions 35' of the side members 34 defining the slots 36 have good thermal contact with surface portions 45' of the rib positioning part 38 next to it. This surface portion 35' is parallel to outer surface portions 43 of the side members 34 to which the cooling means 40 is connected; hence, being the closest surface to the cooling means, it plays a key role in the cooling process.

Preferably, as best seen in FIG. 5, a thermally conductive connecting material 44 is inserted between the rib positioning part 38 of the masking ribs 37 and the surfaces 35, 35' defining the slots 36 in the frame 31 thereby thermally connecting the masking ribs 37 to the cooling means 40 with greater, unquestioned, efficiency. A suitable connecting material 44 is graphite dust or other metal in particulate form. The connecting material 44 may also be a relatively non-volatile fluid or may be contained in a non-volatile base for ease of application. For example, the connecting material 44, in this state, may be rubbed on the surface portions 45 and 45' (the main surface portion) defining the rib positioning parts 38 of the ribs 37, prior to inserting the ribs 37 in the slots 36.

The masking ribs 37 may have any desired cross section, as shown, for example, in FIG. 4. As shown, it will be seen that the main masking part 46 of a rib 37 may be narrower than the width of the slot 36, that one face of a rib 37 may be aligned with the right or left edge of the slot; that by reversing a rib end for end, a different location of the main masking part 46 of such rib 37 may be obtained; and, that the main masking portion 46 of a rib may be offset from the center line between the slots 36 in which a rib 37 is positioned to provide different patterns.

it may readily be seen from these examples that a wide variety of spacings may be obtained with a single frame 31 and a small assortment of ribs 37 and that the ribs themselves can take many shapes.

Because the ribs 37 may be slidably positioned in the slots 36 with the bottom surface portions of the rib positioning parts 38 of the ribs 37 in abutting contact with bottom surface portions 47 of the side members 34 defining the slots 36 to lock the ribs in position with respect to the web 10, the frame 31 may be fixedly positioned exactly where required. Although the frame 31 is shown conforming to a drum surface, the masking means 30 itself is suitable for essentially fiat backup surfaces. The ribs 37 are shown as of essentially the same cross section width; they may be tapered, if desired.

The ribs 37 of this invention are rigid, rugged items. The height at the center may be one-fourth inch for a short rib, and perhaps five-eighths inch or more for longer ribs. The height at the frame may be 2 inches or more.

Typical slitted margin widths resulting from the ribs are one-sixteenth inch and three twenty-seconds inch width, used to prepare one and two-side metallized films.

By using the novel vapor masking means of this invention with its interchangeable ribs defining the desired patterns and with the interchange being efficient and operatively certain, effective metallizing of webs for various uses is made possible.

I claim:

1. An apparatus for vacuum metallizing a web of sheet material comprising:

a vacuum chamber;

a web supply source, a web windup roll and means to move the web from the supply source and onto the windup roll;

a vapor supply source including a crucible containing material located within the chamber;

means to vaporize the material in the crucible to form vapor adapted, upon evacuation of the chamber, to coat an exposed surface of the web as the web is moved past the crucible;

a vapor masking means positioned between the vapor supply source and the web being coated, such masking means consisting of:

a heat conductive frame having front and back members connected to opposed side members, each of the side members having inner surface portions defining spaced, vertically extending slots therein and the frame being positioned adjacent to and a predetermined distance from the web,

heat conductive cooling means connected to outer surface portions of the side members,

heat conductive vapor masking ribs each having surface portions defining rib positioning parts slidably positioned in opposed slots in the side members to lock the masking ribs in position with respect to the web and in which the center line of the main masking part of the masking rib is offset from the center line between the slots in which it is positioned,

the surface portions defining the slots and defining the rib positioning parts being in thermal contact with each other whereby the ribs and the frame are cooled by the cooling means connected to the side members, and

a heat conductive connecting material inserted between the rib positioning parts of the masking ribs and the inner surface portions of the side members defining the slots thereby thermally connecting the masking ribs to the cooling means.

2. The apparatus of claim I wherein the connecting material is in particulate form.

3 The apparatus of claim 2 wherein the connecting material is contained in a non-volatile oil.

4. The apparatus of claim 1 wherein the surface portions of the side members defining the slots include main surface portions parallel to the outer surface portions of the side members to which the cooling means are connected.

5. The apparatus of claim I wherein the side members each have bottom surface portions for locking the masking ribs in position with respect to the web.

6. The apparatus of claim I wherein the connecting material is graphite.

7. The apparatus of claim I wherein the connecting material is a non-volatile fluid.

* t i i 

2. The apparatus of claim 1 wherein the connecting material is in particulate form.
 3. The apparatus of claim 2 wherein the connecting material is contained in a non-volatile oil.
 4. The apparatus of claim 1 wherein the surface portions of the side members defining the slots include main surface portions parallel to the outer surface portions of the side members to which the cooling means are connected.
 5. The apparatus of claim 1 wherein the side members each have bottom surface portions for locking the masking ribs in position with respect to the web.
 6. The apparatus of claim 1 wherein the connecting material is graphite.
 7. The apparatus of claim 1 wherein the connecting material is a non-volatile fluid. 